Method for amplifying three-phase high-frequency power



- March 15, 1927.

G. c. SALMONS METHOD FOR AMPLIFYING THREE-PHASE HIGH FREQUE NOY POWER Filed Feb.20, 192s 2 Sheets-Sheet 1 Q INVEVNTORI 8.201 (l 5mm,

March 15 1927.

" G. c; SALMONS METHOD FOR AMPLIFYING THREE-PHASE HIGH FREQUENCY POWER 7 2 Sheets-Sheet 2 Filed Feb. 20, i926 v INVENTOR eazge G. 5mm,

ATTORNEY Patented Mar. 15,

UNITED STATES PATENT OFFICE.

GEORGE C. SALMONS, OF WEST BRIGHTON, YORK, ASSIGNOR TO WIRED'RADIO,

ING, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

METHOD FOR AMPLIFYING THREE-PHASE HIGH-FREQUENCY POWER.

Application filed February 20, 1926. Serial No. 89.800.

My invention relates broadly to three phase high frequency systems, and more particularly to a system for amplifying three phase high frequency currents and deliveringdthe amplified current to a three phase 0a One of the objects of my invention is'to provide an electron tube amplification systemifor' three phase high frequency currents wherein a minimum number of electron tubes are required for increasing the amplitude of three phase current and supplying the amplified current to a load current.

Another object of myinvention is to provide a balanced electron tube amplifier system for amplifying the power of all of the phases of a three phase high frequency current source and supplying the amplified power to a three phase load.

Still another object ofmy invention. is to provide a circuit arrangement for the amplification of three phase high frequency currents wherein a. pair of balanced electron tubes have their input circuits coupled through open delta connected transformers with a three phase current source, and theirlowing by reference to the accompanying drawings, in which: a

Figure 1 is a diagrammatic view illustrating the-principle of my invention showing a balanced electron tube amplification system for amplifying all of the phases of a three phase source and delivering the three phase high frequency current to a three phase load; Fig; 2 illustrates one embodiment of,

the intermediate tuned circuit between the amplified three phase high frequency current and the three phase load; and'Fig. 3

, illustrates a transmission system embodying the'three phase high frequency currentamplifier of my invention and showing a .modulation circuit in connection therewith.

Heretofore in theart of generating ,and amplifying three phase high frequency power, it has been usual to raise the power level of each phase individually, namely, to employ one amplifier tube or one set of amplifier tubes for each'of the three phases.

Such systems are disclosed in co-pending applications of Robert 1). Duncan, J in, Serial No. 1,374, filed January 9, 1925, now Patent 1,578,881, dated March 30, 1926; Serial No.

61,019, filed October 9, 1925 Serial No.

65,125. filed October 27, 1925; and others.- The chief disadvantage of such systems is the multiplicity of tubes required.

The system of circuits disclosed in the present invention effects amplification of three phase high frequency power with a minimum number of amplifier tubes. I provide a combination of a balanced two tube type of high frequency power amplifier with the so-called ope'n delta connection of transformers for effecting power amplification for use in connection with wired radio transmission over three phase electric power transmission lines.

Referring to the drawings in detail and particularly to Fig. 1, reference character 1 represents a source of three phase high frequency current which may be modulated or unmodulated as the case may be. Connections 2, 3, 4, extend from source 1, the three phases being formed between 2 -3, 3-4 and 4-2. Connected respectively between 2, 3,

and 3, 4, are, primary inductances 5 and 6 of transformers 7, 81 Inductively coupled to primaries 5, 6, are secondary induetances 9, 10; No coupling is assumed to exist between inductance pairs 56 anjd 910 Inductanc'es 9-1O are connected in series in the proper manner, the free terminals respectively connecting with grids 11, 12, of

tubes 13, 14. The common point of connection of inductances 9, 10, is connect d I through biasing battery 15 to common fi1a-.

fne-nt connection'lG which ma be grounded at 17. Plates 18, 19,0f tu e 13, 14, are interconnected through primary induetancee 20, 21, of output transformers 23, 24. The common point of connection is shown connected with the positive terminal of plate battery 22, the negative terminal of whichis connected with common filament connection 16. Inductively coupled to primary inductances 20, 21, are secondary inductances25, 26, which are connected in series. Leads are brought out from the three terminals of inductances 25, 26, which connect through capacities 27, 28, 29, to the three phase electric power transmission line 30. No coupling is assumed to exist between the inductances airs 2021 and 2526.

In ig. 2 variable inductances 31 and 32 are shown connected in series respectively with secondary inductances 25 and 26. Only inductances 25 and 26 are assumed to be coupled with inductances 20 and 21. The three connections to these inductance pairs, as with Fig. 1, contain in series variable capacities 27, 28, 29, and connect with points 33, 34, 35, of the circuit composed of primary inductances 36, 37 38, of transformers 39, 40, 41. Inductances 36, 37, 38 form a closed circuit containing in series variable capacity 42. Inductively coupled to inductances 36, 37, 38, are secondary inductances 43, 44, 45, which are shown connected in Y in the three phase manner. The free terminals of inductances 43, 44, 45 are respectively, connected in series with variable inductances 46 47, 48, variable condensers 49, 50, 51, to a three phase electric power transmission system not shown.

In Fig. 3, 52 represents in entirety a source of unmodulated single phase high frequency current which operates into phase displacing circuit 5310f a type described in copendmg applications, Serial Nos. 1,374 and 61,019 filed respectively, Jan. 9, 1925 and Oct. 7, 1925. Inductively coupled at transformer 54 are seconda inductances 9, 10, which correspond to 1i e numbered inductances of Fig. 1. As with the circuit of Fig. 1, inductances 9, 10, form the input circuits of amplifying tubes 13, 14, the plate circuits of which are interconnected through series connected inductances 20, 21, capacities 55, 56, and common connection 57. Plates 18, 19, derive their requisite high positive continuous voltage from source 58, here shown to be a D. C. generator negative terminal grounded at 17, through high frequency choke coils 59 and low frequency choke coil .60. Choke coils 59 and condensers 55, 56,

function to prevent the passage of continuous current through output mductances 20, 21, and of high frequency alternating current back into 58 and apparatus connected thereto. Connected to the junction between choke coils 59 and .60 are the parallel connected plates of tubes 61 and 62, of which the filaments and grids are also con nected in parallel. One filament connected tery 70. Inductively coupled'to output inductances 20, 21. are secondaryinductances 71, 72, each of which in connected 1n series with variable inductances 73, 74. As

before, the three terminals of these secondary inductances are connected to the three conductors of a three phase electric power transmission line 30, through condensers 75,

76-, 77. No coupling is assumed. to exist between the paired mductances 20, 21, and 71. 72. a

Referring again to the circuit of Fig. 1, which may be considered as typical, it will be observed that three phase high frequency source 1 operates int the primary windings of transformers 7 and 8, of which both the primary and secondary coils are'connected in open delta. The same is true with the output transformers 23 and 24 connected in the plate circuits of the tubes. From the fundamental theory of alternating current circuits it will be noted that if, under the proper conditions, the primary coils of two transformers are connected in series across the three conductors of a three phase feeder, i. e., in open delta, the voltages generated between the three terminals of the two secondary coils'which are also connected in series or in open delta, and, when properly connected, are displaced in phase by 120 degrees. The circuits of Figs. 1, 3, disclose methods utilizing open delta connectedtransformers in conjunction with the balanced type of electron tube amplifier for obtaining three phase high frequency power amplification with the minimum number of tubes. The mathematical theory of the operation of the circuits is given in the following:

Let V and Y respectively, represent the instantaneous values of the voltages developed in secondaries 9 and 10 and impressed between grid and common filament connection 16 of tubes 13 and 14. Now since transformers 7, 8, are connected in open delta and are supplied from three phase current source 1, V and V are displaced in phase by 120 degrees. Assuming they are of equal amplitude, they are written in the form (1) V E sin wt.

(2) Vg2 E SlIl (wt.120).

The law of the electron tube amplifier may be expressed in the usual form plate and V and V as defined. v a and [L are constants of the tubes.

2 2,.V,,E sin (wt 120? The fundamental frequency terms of expressions (5) and (6) are, respectively (7) QMVDE sin mt QILVPE sin (mt-120 developed. Now in a delta connected threev phase system in considering the phase relations of the different voltages it is necessary to adopt a given direction in passing through the circuits as positive to give to the various voltages their proper signs in accordance with this assumed positive direction. In Fig. 1, the direction A*B- C- A is assumed to be positive. The voltage between AB is given byexpression (7); the voltage between BC is given by expression (8) .The voltage between AC isobtained byproceeding from C to A through inductances 20, 21, and is given by -[2p.V E{sin wt+sin (wt-120) (.9) =2 vfa sin (wt-240) or the voltages developed respectively between points A-B, BC and CA are displaced in phase by 120 as with source 1. The voltages developed in the open delta connected secondaries 25, 26, due to transformer action, arealso displaced in phase by. 120 and hence, three phase voltages are impressed in transmission line 30.

The next to the last terms of expression (5) and (6) are of twice the fundamental frequenc i. e., are second harmonic terms displace from each other in phase by 240. Referring again to Fig. 1, the second harmonic voltage generated in primary. 20 or between points AB is' given by,

' 2 2 (10) g? cos 2wt and in primary 21 or between points BC cos (2wt2.40)

Similar to the fundamental frequency amplifying three phase high -frequency power with a minimum number of electron Substituting equations (1) and (2) in (3) and (4),.there results cos 2nt+2wV E sin wt) cos (2wt 240) component voltages, the second harmonic voltage between points AC is That is, these volta es also have their phases displaced by 120, owever', the double frequency voltages appearing between points BC and-CA respectively lag thedouble frequency case with the fundamental frequency components.'

Due to transformer action at 20-25 and 2l26, the; second harmonic or double fre-- quency voltages will appear in the transmission line 30. y I

The circuit of Fig. 1 presents a means of tubes. i.

' In Fig. 2 the secondary inductances. 25 and 26, each containing a variable inducvoltage. between AH by 240-and 120 instead of by 120 and 240 as is the tance 31 and 32 in series, are connected in open delta and operate into inductances 36, 37 and 38, which are connected through variable condenser 42 in closed delta. Induce tively coupled to inductances 36, 37 38, are Y connected inductances 43, 44, 45, which in turn operate into the final load circuit through variable inductances 46, 47, 48, and

variable capacities 49, .50, 51. The circuit of Fig. 2 shows a method for transferring at three phase from open to closed delta and then to Y connection, an expedient which has a very practical value.

The circuit of Fig. 3 shows. a complete 'arrangementlforobtaining three phase high frequencycurrent from a source of single a phase energy, utilizing open delta connected transformer and the balanced double tube type of power amplifier as disclosed in Fig. 3

1, and showing in' addition means for mo'du- "latin the output ofthe amplifier tubes. In

. this gure secondary inductances 9 and 10,

connected in open delta, .are placed in a rotating magnetic field established by phase displacing circuit 53. Three voltages are embodiments of my invention, I desire that frequency output of the tubes 13, 14, through the action of iron core inductance 60. Plate modulation isshown in Fig. 3 althouglrit will be understood that grid modulation may be employed, and it is not intended to so limit the scope of this invention. I Secondary inductances 71, 72, containing variable inductances 73 and 74 in series, are connected in open delta and operate into the three phase transmission line 30.

' While I have described certain preferred it be understood, that modifications can be made and that I intend no limitationsupon the invention other than are imposed by the scope of the appended claims. i

What I claim and desire to secure by Let:

ters Patent of the United States is:

r 1. In a system for amplifying three phase high frequency power, the combination with a spurce of three phase high'frequency cur ,rent, a pair of electron tubes connected in balanced relationship, input and output circuits for. saidtubes, an open delta'transformer system connected in'said input circuits for impressing energy from said source upon said electron tubes, a load circuit, and

* quency means for impressing three phase high frecircuits upon said load circuit.

2. In-a system for amplifying three phase high frequency current, the combination of a source of three phase high frequency cur- 7 rent, a pair of electron tubes rhaving input and out ut circuits connected imbalanced relations ip," open -delta' connected trans- -formers couplin said input circuits with said source of. igli' frequency current, a.

load circuit, and. open delta connected transformers interposed between said output cir: cuits and said load circuit for impressing three phasehigh frequency current upon said load circuit.

3. In a system for amplifyihg three phase high frequency current, the combination with a sourceof three phase-high frequency current, a pair of balanced electron tube circuits, a load circuit, and means connected between said electron tubes and said load circuit for impressing three phase high frequency current upon said load circult, said electron tube circuits operating to ncrease the amplitude of said three phase high frequency current. O V

.4. In a system for am lifymg three phase high frequency power, t e combination w1th current derived from said output high frequency current, the combination 7 with a source of three phase high frequency current, a balanced electron tube system including a. pair of ele ctron tubes, each having input and output circuits, open delta connected transformers coupling said input circuits with said source, a load circuit, and a composite open'and closed delta transformer system coupling said output circuits with said load circuit for delivering ampli fied three phase high frequency current to said load circuit. V

6. Ina system for amplifying three phase high frequency current, the combination with a source of three phase high frequency current, a pair of electron tubes connected in balanced relationship, said tubes having input and output'circuits, open delta connected transformers interposed between said source and the input circuits of said electron tubes, a load circuit, an intermediate tuned circuit connected with said circuit,

and delta connected transformers coupling connected transformers connected in the output circuitsof said electron tubes, an inter- 120 mediate circuit connected with said delta connected transformers, and a Y connected system for establishingconnection between said intermediate circuit and said load circuit for impressing three quency current upon said load circuit.

8. In a system for amplifyingthree phase high frequency current, the comblnatlon with a source of three phase high frequency current, a pair of electron tubes connected 1n balanced relationship, said tubes having-input and output circuits, a source of three phase high fre phase high, frequency current, en delta connected transformers interpose between said source and the input circuits of said electron tubes, a load circuit, open delta connected transformers connected in the output circuits of said electron tubes, open delta connected transformers interposed in th' output -clrcults of said electron tubes,

an intermediate c rcuit connected with said last mentioned open delta connected trans-- formers, an additional set of transformers cuits, and connections between said last'menhaving their primary windings connected in closed delta to .saidintermediate circuit and their secondary windings connected in Y to said load circuit for impressing threesaid tubes, an inductance included in eachof said circuits, a pair of inductances coupled with the inductances in said input cirthe com ination with tioned pair of inductances and said sourceof three phase high frequency current, a load circuit, an intermediate tuned circuit connected with said load circuit, and a pair of inductances connected in said intermediate circuit and coupled respectively with the inductances in the output circuits of said electron tubes whereby amplified three phase high frequenc current may be impressed upon said 10a circuit.

10. In. asystein for amplifying three phase high frequency power, the combmation of a source of three phase high frequency current, a pair of electron tubes each having filament, grid and plate electrodes,

input circuits comprising a pair of transformers with primary and secondary windings connected in open delta for associating said grid electrodes with said source, output circuits comprising a pair of transformers with primary and secondary windings connected in open plate electrodes, a three phase electric power distribution circuit constituting a load circuit and connections between said load cir- -cuit and said output circuits for impressmg amplified three phase high frequency current on said load circuit.

GEORGE OQSALMONS,

delta associated with said 

